Have you tried hydraulic ram suppliers and rebuilders? This material is their daily bread.

Alternatively, what about gas struts for toolboxes, hatchback car doors, etc.?

Once you get under the chrome, the rod is easy to machine. You could grind it off gently if you cannot turn it off.

Or use stainless. Everyone seems to go for stainless spokes on the wheels. Not much side load on a shock, its all up & down.

Steve.

You might be able to fake it with a bit of stainless rod, good enough for the kind of miles most restored tiddlers do.

What kind of 50cc bike is it? Pics?

Price and availability may be the limiting factors, but 440 stainless may be preferable if opting for stainless. It is high carbon and harder and stronger than most of the commonly available varieties. It is also available as precision ground rod ( if that is a requirement ).

In chromed steel there is a lot of options available ex China and probably many other places as it is sold for guide rails for 3D printers and CNC machinery. Supply ex China ( Aliexpress ) may be problematic at the moment but some suppliers with warehouses may be able to help. Checking with local suppliers to confirm that they have the material in stock would be recommended.

Pero

Hi C J. Up to 1" or 25mm I use 5C collets to hold the rod, bigger stuff is usually in soft jaws in the three jaw chuck.